package com.lagou.sqlSession;

import com.lagou.pojo.Configuration;
import com.lagou.pojo.MappedStatement;

import java.beans.IntrospectionException;
import java.lang.reflect.*;
import java.sql.SQLException;
import java.util.List;

public class DefaultSqlSession implements SqlSession {
    private Configuration configuration;

    public DefaultSqlSession(Configuration configuration) {
        this.configuration = configuration;
    }

    @Override
    public <E> List<E> selectList(String statementid, Object... params) throws IllegalAccessException, IntrospectionException, InstantiationException, NoSuchFieldException, SQLException, InvocationTargetException, ClassNotFoundException {
        SimpleExecutor simpleExecutor = new SimpleExecutor();
        MappedStatement mappedStatement = configuration.getMappedStatementMap().get(statementid);
        List<Object> list = simpleExecutor.query(configuration, mappedStatement, params);
        return (List<E>) list;
    }

    @Override
    public <T> T selectOne(String statementid, Object... params) throws Exception {
        List<Object> objects = selectList(statementid, params);
        if(objects.size() ==1){
            return (T) objects.get(0);
        }else{
            throw new RuntimeException("查询结果为空或返回结果过多");
        }
    }

    @Override
    public Object executeCUD(String statementid, Object... params) throws Exception {
        SimpleExecutor simpleExecutor = new SimpleExecutor();
        MappedStatement mappedStatement = configuration.getMappedStatementMap().get(statementid);
        simpleExecutor.executeCUD(configuration, mappedStatement, params);
        return null;
    }


    @Override
    public <T> T getMapper(Class<?> mapperClass) {
        //使用JDK动态代理来为Dao接口生成代理对象，并返回

        Object proxyInstance = Proxy.newProxyInstance(DefaultSqlSession.class.getClassLoader(), new Class[]{mapperClass}, new InvocationHandler() {
            @Override
            public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
                //底层都还是去执行JDBC代码 //根据不同情况，来调用selectList或者selectOne
                //准备参数 1：statmentid :sql语句的唯一标识：namespace.id=接口全限定名.方法名
                //方法名： findAll
                String methodName = method.getName();
                String className = method.getDeclaringClass().getName();
                String statementId =className+"."+methodName;

                //准备参数2：params:args
                //获取被调用方法的返回值类型
                 Type genericReturnType =method.getGenericReturnType();
                 String typename =genericReturnType.getTypeName();
                 if(typename =="void"){//根据返回值名称判断是否为void  无返回值类型
                     return executeCUD(statementId,args);
                 }else{
                    //判断是否进行了 泛型类型参数化   （就是参数有没带泛型）
                    if(genericReturnType instanceof  ParameterizedType){
                        List<Object> objects = selectList(statementId, args);
                        return objects;
                    }

                    return selectOne(statementId,args);
                 }
//                if(type == typeof(void.class) ){//判断返回值类型是否为空， 不为空时为查询类型
//                    //准备参数2：params:args
//                    //获取被调用方法的返回值类型
//                    Type genericReturnType = method.getGenericReturnType();
//                    //判断是否进行了 泛型类型参数化   （就是参数有没带泛型）
//                    if(genericReturnType instanceof  ParameterizedType){
//                        List<Object> objects = selectList(statementId, args);
//                        return objects;
//                    }
//
//                    return selectOne(statementId,args);
//                }else{//返回值类型为空
//                    return executeCUD(statementId,args);
//                }


            }
        });
        return (T) proxyInstance;
    }
}
